The act of expression in the case you brought forward earlier is taking a toilet seat out of its context. That does trigger an intellectual reaction with at least some of the observers and is done so for exactly that reason. Come to think of it, it might also trigger an emotional reaction (like disgust or something). Hence, it is art. At least according to my definition ^^

Consider the possibility that the Dadaists failed in their attempt to create anti-art. Or have to had come to the conclusion that anti-art is not not art.

Although the outset of the Dadaists was to counter exsisting (art-) culture, I don't think they succeeded in rising above or falling below the abstract concept of art as such

I didn't say that the artist needs to be of the opinion that his art is or must be considered art. It is up to the observers to decide. The only requirements I can give to an artist is that his work needs to have been made predominantly in the function of triggering some response. Which, in my opinion, certainly holds true for Dadaists. Even if their underlying message was art/civilization is dead, that's still triggering response.

Correct me if I am wrong. but my hazy art memory tells me that Dada was more of a sign of society at the time? After the horror of WW1, it was a nihilistic concept thrown in the face of society, to show the true nature of the time honoured moral concepts that were swept away by total war. At least in the works of Grosz and Dix.

I think that who and how it was produced can enhance a work of art, but should not be the sole basis of why it is appreciable. For example, the art of Francisco de Goya would still be of good quality even if the Spanish inquisition had never occurred. The visual style of the paintings evoke all sorts of emotions and imagery, but the fact that they were based on real events enhance this quality significantly.